KR100212970B1 - Cobalt recovery method - Google Patents

Abstract

The present invention relates to a method for recovering cobalt from waste, and more particularly, in order to recover and recycle expensive cobalt compounds used as catalysts in the malonic acid ester manufacturing process, first, the cobalt-containing waste solution is treated with an aqueous alkali solution. It relates to a method of inducing precipitation and recovering high-purity cobalt by selectively depositing cobalt oxalate by adding oxalic acid or oxalic acid hydrate to an acid solution in which primary precipitates are dissolved.

Description

How to recover cobalt from waste liquid

The present invention relates to a method for recovering cobalt from waste, and more particularly, in order to recover and recycle expensive cobalt compounds used as catalysts in the malonic acid ester manufacturing process, first, the cobalt-containing waste solution is treated with an aqueous alkali solution. It relates to a method of inducing precipitation and recovering high-purity cobalt by selectively depositing cobalt oxalate by adding oxalic acid or oxalic acid hydrate to an acid solution in which primary precipitates are dissolved.

Generally, cobalt compounds are expensive metals that depend entirely on imports, and are used for alloys, pigments and dyes, paint desiccants, additives, and catalysts.In particular, catalysts such as aldehydes and alcohols are used as olefins in petrochemical fields. It is useful for carbonylation, oxidation, etc. in the field of synthesis or organic synthesis, and is mainly used in the form of cobalt-carbonyl compound.

Cobalt recovery can be recovered in a form that can be recycled by converting between cobalt compounds. For example, cobalt sulfate, cobalt acetate, cobalt nitrate, etc. can be obtained from cobalt alloys or waste cobalt compounds, or Therefore, recovery to cobalt oxide, cobalt metal, and the like is also possible.

Currently, cobalt recovery technology is continuously developed at home and abroad, and the amount of recovered cobalt is increasing. However, recovery to high-purity catalysts is difficult to realize due to the difficulty in technology and complexity of the process. In particular, in the malonic acid ester synthesis process, which is the object of the present invention, various heavy metals are contained in the by-product waste liquid after use, in addition to the cobalt used as a catalyst, which causes environmental pollution when released without removing them. .

In general, techniques for recovering cobalt from the waste liquid include ion exchange, solvent extraction, precipitation, and the like.

First, the ion exchange method [US Pat. Nos. 3,488,184, 5,002,645] is a method of recovering cobalt by ion bonding and desorption with a resin using an ion exchange resin, etc., in which a large amount of salt and metal ions are contained in the waste liquid. If present, there is a disadvantage in that ion exchange is inefficient and a large capacity ion exchanger is required.

Second, the solvent extraction method [Korean Patent Application No. 94-5180] extracts cobalt from the waste liquid by using the selective extraction capacity of the solvent. By controlling the composition of the solvent, cobalt can be recovered relatively purely from a mixture of various metals. On the other hand, as the extraction continues, there is a disadvantage in that the extraction capacity is reduced due to the contamination of the solvent and the size of the extraction equipment is large.

Third, the precipitation method [European Patent Application No. 0666108] is obtained by converting into an insoluble salt in an aqueous solution, followed by filtration, and then obtaining a filtration process. Incorporation of impurities by coprecipitation makes it difficult to recover products of high purity. In particular, when a large amount of inorganic salts and metals such as nickel and iron are mixed, it is difficult to recover high-purity cobalt compounds that can be recycled as a catalyst due to coprecipitation. It is being recovered as a product.

The present invention is an economical and relatively simple process to remove impurities such as sodium, iron, nickel, and recycled as a catalyst by applying a fine sedimentation method for the recovery of cobalt waste catalyst by-produced in the malonic ester production plant The purpose is to provide a method for recovering only cobalt.

The present invention is a method for recovering cobalt dissolved in the waste liquid,

(1) forming a primary precipitate by adding an alkaline solution to the cobalt-containing waste liquid discharged from the malonic acid ester synthesis process;

(2) dissolving the primary precipitate in an aqueous acid solution,

(3) a process of recovering cobalt oxalate produced by adding oxalic acid to the solution.

Referring to the present invention in more detail as follows.

The present invention relates to a method for recovering cobalt that can be recycled from waste liquid discharged from a malonic acid ester manufacturing process using a secondary precipitation method.

In the present invention, the waste liquid refers to waste liquid discharged from the process of preparing malonic acid ester by reacting acetic acid ester, cobalt catalyst, alcohol and carbon monoxide. In such waste liquid, a small amount of organic substances such as malonic acid, alcohol having 1 to 3 carbon atoms, malonic acid ester and toluene in aqueous solution are present, and cobalt (500 to 10,000 ppm), iron (10 to 500 ppm), nickel as metal components (10 ~ 500 ppm), etc. In addition, inorganic salts such as salt and forget-me-not are dissolved in a large amount by almost 30% by weight.

When the cobalt compound is recovered from the waste liquid by the precipitation method, it is first necessary to switch to a state of a primary precipitate that can be precipitated in an aqueous solution, that is, cobalt hydroxide, cobalt carbonate or the like. Therefore, the waste solution is stirred at 50 to 500 rpm to control the reaction rate, and an alkaline aqueous solution is added to induce precipitation of cobalt hydroxide to perform the first precipitation reaction. Here, the reason why the aqueous alkali solution is used is that the solubility of the cobalt to be recovered can be lowered because the solubility of the alkali metal salt is large. Such aqueous alkali solution is an aqueous salt solution of an alkali metal such as sodium, potassium, calcium, and the like, for example, sodium hydroxide, sodium carbonate and the like. The aqueous alkali solution is added until the pH of the waste liquid is 10 to 13, preferably until the pH is 11 to 12. The resulting primary precipitate is filtered with a vacuum filter and then washed with 50-100 ml of distilled water.

However, when impurities such as forget-me-not and salt are present in the waste liquid at a high concentration, the primary precipitate has a problem in that the purity is lowered due to coprecipitation of the impurities, and thus the purity required for recycling as a catalyst cannot be obtained.

Therefore, in order to solve this problem, the present invention is to dissolve the primary precipitate in an aqueous acid solution, and then add oxalic acid or a hydrate thereof, and stir and mix the mixture at 50 to 500 rpm, thereby selectively removing 2 from the impurity mixture. Precipitate and separate only the primary precipitate, cobalt oxalate.

At this time, the acid aqueous solution is used 5% to 50% sulfuric acid solution, or 20 to 95% concentration of acetic acid solution to smoothly dissolve the cobalt hydroxide and maximize the recovery rate in the secondary precipitation. However, if the sulfuric acid aqueous solution is used as the acidic aqueous solution, if the sulfuric acid aqueous solution of less than 5% concentration is used, there is a problem in that the primary precipitate is not dissolved smoothly. The disadvantage is that the recovery rate is low, which is not preferable. In addition, when using an acetic acid aqueous solution as an aqueous acid solution, the use of less than 20% concentration out of the above range is difficult to dissolve the primary sediment, whereas when used in excess of 95% concentration is a problem of poor filterability of the recovered product Occurs.

In addition, oxalic acid used for secondary precipitation can be selectively precipitated by reacting with cobalt to produce cobalt oxalate, and both hydrates and anhydrides thereof can be used for oxalic acid. In addition, the amount of the cobalt ion is preferably used in an amount of 1.0 to 2.0 equivalents, and if the addition amount is less than 1.0 equivalents, there is a problem that the recovery rate is lowered, whereas when the amount exceeds 2.0 equivalents, there is a problem that the purity of the recovered product is lowered. Not desirable

In addition, the secondary precipitation reaction is preferably carried out at a temperature condition of 10 ~ 70 ℃, if the reaction is carried out below 10 ℃, there is a problem in the purity of the recovered product, also if the recovery exceeds 70 ℃ It is not preferable because there is a problem.

Here, cobalt oxalate precipitated secondly is an insoluble compound in an aqueous acid solution, and is excellent in particleability, and thus, precipitates can be easily separated by filtration and also easy to clean and minimize incorporation of impurities.

Finally, the cobalt oxalate precipitated above is dried for 2 to 4 hours using a dryer at 50 to 80 ° C to complete the present invention.

The cobalt oxalate recovered above is dissolved in an acid solution such as nitric acid and hydrochloric acid and a basic solution such as ammonia water to be converted to another salt or calcined to obtain a cobalt compound of various uses and forms.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by Examples.

Example 1

To 1 liter of the waste solution of the composition as shown in Table 1 was added 25% aqueous sodium hydroxide solution with stirring until reaching pH 12. Then, the cobalt hydroxide began to form rapidly when the pH value reached 8, and the stirring was continued for 30 minutes at the stirring speed of about 400 rpm. The resulting precipitate was filtered with a vacuum filter and the resulting filtrate was washed with 100 ml of distilled water. The obtained cobalt hydroxide was redissolved in 200 ml of 30% sulfuric acid aqueous solution to obtain a cobalt sulfate aqueous solution. 15 g of hydrate of oxalic acid was added thereto, followed by stirring for 30 minutes at a stirring speed of 400 rpm at 50 ° C. Next, the resulting solid was dried for 4 hours at 60 ℃ hot air dryer to obtain a yellowish pink 10.7g of cobalt oxalate dihydrate. At this time, the components and contents of the waste liquid used as the recovery object, the cobalt hydroxide obtained by primary precipitation, and the cobalt oxalate obtained by secondary precipitation, are shown in Table 1, Table 2, and Table 3, respectively.

Composition of waste liquid ingredient cobalt iron nickel calcium Inorganic salts Organic matter water content 0.35% 230 ppm 100 ppm 43 ppm 21% 1.5% 77.2%

The composition of the primary sediment ingredient cobalt salt iron nickel calcium content 17.3% 27.7% 156 ppm 72 ppm 42 ppm

Composition of secondary precipitate ingredient cobalt salt iron nickel calcium content 32.7% 0.08% 28 ppm 10 ppm 10 ppm

Examples 2-6

In the same manner as in Example 1, except that the waste liquid, the primary precipitate and the secondary precipitate used as the recovery targets are shown in Tables 4, 5 and 6, respectively.

Composition of waste liquid division Example 2 Example 3 Example 4 Example 5 Example 6 cobalt 0.35% 0.10% 0.85% 0.35% 0.22% iron 230 ppm 175 ppm 210 ppm 460 ppm 210 ppm nickel 50 ppm 23 ppm 58 ppm 48 ppm 384 ppm calcium 43 ppm 36 ppm 47 ppm 51 ppm 43 ppm Inorganic salts (salt + forget-me-not) 11% 27% 29% 21% 27% Organic matter 1.5% 10.0% 3.4% 1.2% 1.0% water 87.0% 62.5% 76.5% 77.4% 71.4%

The composition of the primary sediment division Example 2 Example 3 Example 4 Example 5 Example 6 cobalt 18.2% 11.6% 9.80% 17.3% 10.3% salt 28.0% 32.1% 32.2% 27.7% 31.8% iron 183 ppm 162 ppm 223 ppm 382 ppm 254 ppm nickel 52 ppm 22 ppm 79 ppm 32 ppm 179 ppm calcium 20 ppm 11 ppm 32 ppm 11 ppm 32 ppm

Composition of secondary precipitate division Example 2 Example 3 Example 4 Example 5 Example 6 cobalt 32.2% 31.9% 32.5% 32.8% 32.3% salt 0.17% 0.13% 0.22% 0.09% 0.20% iron 30 ppm 26 ppm 42 ppm 56 ppm 35 ppm nickel 10 ppm 10 ppm 10 ppm 10 ppm 21 ppm calcium 10 ppm 10 ppm 10 ppm 10 ppm 10 ppm

Examples 7 to 11: Changes in Components and Contents of Cobalt Oxalate According to Alkali Solution

In the same manner as in Example 1, 25% aqueous sodium carbonate solution was added instead of 25% aqueous sodium carbonate solution to adjust the pH to 12 to obtain cobalt carbonate precipitate to recover cobalt oxalate. The components of the waste liquid are the same as in Table 4, and the components and contents of the obtained cobalt carbonate precipitate and cobalt oxalate are shown in Table 7 and Table 8, respectively.

The composition of the primary sediment division Example 7 Example 8 Example 9 Example 10 Example 11 cobalt 8.56% 9.16% 7.80% 12.4% 8.34% salt 25.5% 24.6% 26.3% 19.9% 25.8% iron 233 ppm 189 ppm 283 ppm 272 ppm 227 ppm nickel 51 ppm 27 ppm 69 ppm 45 ppm 155 ppm calcium 24 ppm 12 ppm 27 ppm 36 ppm 21 ppm

Composition of secondary precipitate division Example 7 Example 8 Example 9 Example 10 Example 11 cobalt 31.3% 31.1% 32.3% 31.7% 31.4% salt 0.15% 0.14% 0.25% 0.14% 0.23% iron 42 ppm 34 ppm 51 ppm 49 ppm 41 ppm nickel 10 ppm 10 ppm 10 ppm 10 ppm 29 ppm calcium 10 ppm 10 ppm 10 ppm 10 ppm 10 ppm

Examples 12-13: Recovery change of cobalt oxalate with temperature change during secondary precipitation reaction

In the same manner as in Example 1 except that the temperature in the process of adding the hydrate of oxalic acid

It adjusted to 30 degreeC and 70 degreeC. To compare the effect of temperature

The result of the secondary intercalation is illustrated in Comparative Example 1. The composition of the used waste liquid and cobalt hydroxide is shown in Table 1 and Table 4, respectively, and the components of the obtained cobalt oxalate are shown in Table 9.

Composition of secondary precipitate division Example 12 (30 degreeC) Example 13 (70 degreeC) Comparative Example 1 (10 ° C) cobalt 31.6% 32.8% 28.1% salt 0.18% 0.12% 0.79% iron 30 ppm 28 ppm 38 ppm nickel 10 ppm 10 ppm 10 ppm calcium 10 ppm 10 ppm 10 ppm

Examples 14-15: Changes of cobalt oxalate according to acetic acid concentration

In the same manner as in Example 1, cobalt hydroxide obtained by primary precipitation

Cobalt oxalate was obtained by dissolving in acetic acid solution instead of sulfuric acid. The composition of the waste liquid and cobalt hydroxide used as a recovery object are shown in Table 1 and Table 2, and the components of cobalt oxalate obtained according to the change of acetic acid concentration (50% and glacial acetic acid) are shown in Table 10.

Composition of secondary precipitate division cobalt salt iron nickel calcium Example 14 (50% acetic acid) 30.7% 0.10% 28 ppm 10 ppm 10 ppm Example 15 (glacial acetic acid) 32.8% 0.06% 20 ppm 10 ppm 10 ppm

Examples 16 to 17: change in cobalt oxalate according to sulfuric acid concentration

In the same manner as in Example 1 except for obtaining cobalt hydroxide

The concentration of aqueous sulfuric acid solution was changed, and cobalt oxalate was obtained by secondary evaporation as shown in Table 11. In order to compare the effect of sulfuric acid concentration, the recovery result in sulfuric acid 70% is illustrated in Comparative Example 2. The composition of the waste liquid and cobalt hydroxide used for the recovery are shown in Table 1 and Table 2, respectively.

Composition and Recovery of Secondary Sediment division Example 16 (10% sulfuric acid) Example 17 (50% sulfuric acid) Comparative Example 2 (70% sulfuric acid) cobalt 32.5% 29.8% 31.2% salt 0.10% 0.62% 0.05% iron 32 ppm 21 ppm 33 ppm Recovery 10.1 g 9.2g 6.1g

As described above, the present invention recovers expensive cobalt compounds from various impurities in the waste liquid in a relatively simple manner, which can be recycled for use in catalysts requiring high purity for activity, and is economical as well as environmental pollution due to heavy metals. There is an effect that can prevent.

Claims (6)

In the method of recovering cobalt dissolved in the waste liquid, (1) forming a primary precipitate by adding an alkaline solution to the cobalt-containing waste liquid discharged from the malonic acid ester synthesis process; (2) dissolving the primary precipitate in an aqueous acid solution, (3) A method for recovering cobalt from waste liquid, comprising the step of recovering cobalt oxalate produced by adding oxalic acid to the solution. The method of claim 1, wherein the primary precipitates are cobalt hydroxide and cobalt carbonate. The method of claim 1, wherein the oxalic acid is in the form of an oxalic acid hydrate or an anhydride thereof, and the amount of the oxalic acid is 1.0 to 2.0 equivalents relative to the cobalt ions. The method of claim 1 wherein the secondary precipitate is one of cobalt oxalate and its hydrate. The method of claim 1, wherein the temperature of the formation of the secondary precipitate is 20 ~ 70 ℃. The method of claim 1, wherein the acid solution is sulfuric acid solution of 5 to 50% concentration or acetic acid solution of 20 to 95% concentration.